docs: def save(self, path=None, filter_name=None):
          """
          Saves this document to a local file system.
  
          The optional first argument defaults to the document's path.
  
          Accept optional second  argument which defines type of
          the saved file. Use one of FILTER_* constants or see list of
          available filters at http://wakka.net/archives/7 or
          http://www.oooforum.org/forum/viewtopic.phtml?t=71294.
          """
  
          if path is None:
              try:
                  self._target.store()
              except _IOException as e:
                  raise IOError(e.Message)
              return
  
          # UNO requires absolute paths
          url = uno.systemPathToFileUrl(os.path.abspath(path))
          if filter_name:
              format_filter = uno.createUnoStruct('com.sun.star.beans.PropertyValue')
              format_filter.Name = 'FilterName'
              format_filter.Value = filter_name
              filters = (format_filter,)
          else:
              filters = ()
          # http://www.openoffice.org/api/docs/common/ref/com/sun/star/frame/XStorable.html#storeToURL
          try:
              self._target.storeToURL(url, filters)
          except _IOException as e:
              raise IOError(e.Message)